Ultrasound systems are used by physicians and medical technicians as a diagnostic tool to view human body structures such as organs and tissues. For example, ultrasound systems provide real-time moving images of the heart and excellent soft tissue images of the abdomen, making ultrasound systems useful for diagnosing heart problems and indispensable for monitoring pregnancies. Images are produced without the harmful radiation of X-rays and without the long image acquisition time of magnetic resonance imaging (MRI).
In order to view a body structure, an electrical signal is generated and propagated via a cable to a transducer which converts the electrical signal into an ultra-high frequency sound (i.e., ultrasound) signal that is aimed at the body structure. The transducer also receives the ultrasound signal after it is attenuated and reflected by the body structure and converts it back into an electrical signal which is carried by the transducer cable to a display processor. The transmitted and received electrical signals are compared by the display processor which then generates an image of the body structure from the compared signals. Any disturbances on the transducer cable will degrade the image of the body structure and may cause faulty diagnoses. The transducer cable must be shielded to prevent electrical sources from interfering with the electrical signals and should be flexible so that the transducer may be easily maneuvered and aimed. Flexibility is especially important in transesophageal echocardiography (TEE) applications in which the transducer is placed down the esophagus to obtain high quality images of the heart.
Unfortunately, prior art transducer cables that are flexible and shielded are also expensive to manufacture and in many ultrasound systems the transducer cable may cost as much to manufacture as the transducer itself. One prior art transducer cable used in Hewlett-Packard Company's HP SONOS 1500 ultrasound system is constructed from many small diameter coaxial wires (36 AWG or smaller) bundled into a cable jacket. This type of transducer cable may be expensive to manufacture because the performance of each coaxial wire relies on a precise concentricity of a center conductor and a outer shield throughout its length.
In accordance with a first illustrated preferred embodiment of the present invention a wound transducer cable is flexible in all directions, shielded and is inexpensive to manufacture. In the wound transducer cable several stripline assemblies are helically wound around a flexible core and a conductive shield is braided over the stripline assemblies and encased in an outer insulating jacket. Signal wires present in the stripline assemblies are shielded by a conductive strip within each stripline assembly and by the conductive shield. In accordance with a second illustrated preferred embodiment of the present invention a stripline transducer cable is flexible and shielded and has a low manufacturing cost. A stack of parallel stripline assemblies, a conducting shield and an insulating jacket are co-extruded to form the flexible stripline transducer cable having many signal conductors. A conducting strip within each stripline assembly and the conducting shield provide shielding for the sensitive electronic signals to be transmitted over the stripline transducer cable. In accordance with a third illustrated preferred embodiment of the present invention, a ribbon transducer cable has the same flexible, shielded and low cost characteristics as the stripline transducer cable. This ribbon transducer cable is constructed from a stack of parallel ribbon assemblies co-extruded with parallel shield conductors and a flexible insulating jacket.